The invention concerns a coating device for coating running paper webs supported by a backing roll, including a doctor element which removes excess coating mixture, a baffle plate located on the entrance side of the paper web relative to the doctor element, a chamber having a mouth for feeding the coating mixture, and an application space defined in part by the doctor element and the baffle plate between the mouth of the chamber and the paper web. Such a coating device is known from the U.S. patent document No. 4,250,211. In these coating devices, the coating mixture is fed from a chamber, pressurized, to an application space which is enclosed on all sides and where a baffle plate on the entrance end exposes relative to the paper web, and respectively the backing roll supporting it, a gap of only such width that a certain pressure of the coating mixture is still maintained in the application space defined in part by the paper web and the doctor element.
It has been demonstrated that specifically in coating very thin papers, but even more so with very low coating weights, for instance basis weights less than 6 g/m.sup.2, a uniform coating is very difficult to accomplish.
The problem underlying the invention is to so fashion the device that also in the case of very thin papers and/or specifically very low basis application weights of less than 7 g/m.sup.2 a uniform coating can be achieved.